Molded caseless small arms ammunition



Oct. 19, 1965 J. B. QUINLAN ETAL 3,212,440

MOLDED CASELESS SMALL ARMS AMMUNITION Filed Feb. 10, 1964 INVENTORS JOSEPH B. QUINLAN MARVIN E. LEVY EARL F.' VA ARTSDALEN United States Patent Ofifice 3,212,440 Patented Oct. 19, 1965 3,212,440 MOLDED CASE ESS SMALL ARMS AMMUNITION Joseph B. Quinlan, Marvin E. Levy, and Earl F. Van Artsdalen, Philadelphia, Pa., assignors to the United States of America as represented by the Secretary of the Army Filed Feb. 10, 1964, Ser. No. 343,904 3 Claims. (Cl. 102-38) (Granted under Title 35, US. Code (1952), see. 266) The invention described herein may be manufactured and used by or for the Government for governmental purposes without the payment to us of any royalty thereon.

This invention relates to a structurally integral, selfcontained small arms round of ammunition having ballistic characteristics possessed by a metal cased round of similar caliber and using the same chemical type propellant therein.

Unsuccessful attempts have been made to satisfy the need for a lightweight caseless small arms round. So far as is known, all prior efforts to make such a molded propellant round have failed in that the ballistic and physical properties obtained therewith were considerably inferior to metal cased rounds of similar caliber.

Among the many advantages of our invention is a saving of weight of about 40% over a similar sized metal cased round. Other advantages to be gained from the practice of our invention are the elimination of the need for extraction (and, in the case of tanks or aircraft, storage space for spent ammunition), higher cyclic rates of fire, and elimination of the need for expensive and critical brass cartridge cases. Obturation for prevention of leakage rearwardly around the bolt and firing pin is provided as described in the patent application of John J. Scanlon, Jr., for Obturation for Small Arms, S.N. 299,437, filed August 1, 1963, now Patent No. 3,166,864.

It is therefore a principal object of this invention to provide a completely caseless round of ammunition yielding ballistic performance substantially the same as a cased round of equal caliber, being light in weight and yet including the aforementioned advantages.

Referring now to the single figure of the drawing wherein a longitudinal section of a preferred embodiment of the invention is shown, our molded propellant has the usual projectile 11 adhesively secured in a recess thereof. The adhesive may be of any well-known combustible type, such as Duco cement, for example, which is a nitrocellulose dissolved in methyl ethyl ketone, and having no deleterious effects upon the molded propellant. The projectile may partake of any suitable small arms type, that shown being a typical jacketed type for receiving the impressions of the lands and grooves to effect stabilization.

An axial cavity 12 is formed within the round and is generally centrally disposed therewithin as shown.

A primer 13 is received within an axial recess 14 of substantially the same diameter as cavity 12 but is separated therefrom by a wall 15 comprising the original integrally molded propellant. The wall 15 supports primer 13 when it receives an impact from a firing pin, not shown. In the case of a 7.62 mm. rifle, the propellant herein will produce a mean projectile velocity of approximately 2750 ft./sec. at a maximum mean pressure of less than 50,000 p.s.i. In short, our primer and propellant are capable of developing an equivalent mass burning rate and ballistic similarity to the same type propellant comprised of loose granules employed in the metal cased round of substantially the same size.

The primer 13 is suitably of the type disclosed in patent application of John J. Scanlon, ]r., et al. for Primer for Consumable Round, S.N. 214,152, filed August 1, 1962,

and containing a lead styphnate type .mix ignited by a percussion cap enclosed between thin sheets of paper. The configurations of some of the original propellant granules are shown at 16.

The outside diameter of molded propellant 10 should be essentially the same as the outside diameter of a metal case, if one were used, and it therefore becomes apparent that more propellant will be present when molded as in our instant invention. However, due to increased chamber volume when compared to metal cased rounds, the additional propellant has been found to provide interior ballistic characteristics comparable to the metal cased rounds.

We have also found that molded propellant 10 requires a greater propellant charge than a similar sized metal cased round in order to produce substantially equivalent ballistic properties. Among the several reasons for the needed increase may be mentioned the fact that about 5% by weight of a suitable binder, such as collodion, for example, is required to hold the granules together. Collodion used herein is a 5% nitrocellulose of 710% nitrogen content, the balance being a 50-50 mixture of ethanol and ethyl ether, and possesses a lower energy content than the propellant granules and a slower burning rate.

Additionally, the primer blast breaks up our molded propellant into individual or aggregative granules exposing surface areas thereof greater or less than the area exposed when unbound granules of a cased round are subjected to a similar blast. Whether the surface area exposed is greater or less in either case is not known for sure but this factor and the aforementioned reason have been determined empirically to warrant the additional propellant granules.

The cavity 12 will be adjusted in size to provide a desired propellant weight to yield the desired ballistics.

The cavity 12 and the recesses which receive primer 13 and projectile 11 may be conveniently molded within the caseless round by well-known and conventional means or machined, the formation thereof constituting no part of this invention.

To reduce heat conductivity from the chamber to the round and thus reducing danger of cook-off, a suitable coating of about 0.001 to 0.0015 inch thick, and not more than 0.002 inch thick, may be sprayed, brushed, etc. over the outer surfaces of molded propellant 10. Two such coatings we have found to work admirably contain about by weight of methyl methacrylate and the balance being either molybdenum disulfide or graphite.

In the process of making our binder described herein, approximately 5% by weight of a low nitrogen nitrocellulose is dissolved in about by weight of a 50-50 solution of ethanol and ethyl ether. About 6 grains by weight of the propellant granules are placed in a steel mold to which about 0.25 cc. of the above binder are added and thoroughly mixed. An additional 6 grains of propellant are added thereto and the same quantity of binder added, and so on until about 80 grains of a semisolid mix is produced. The resultant mass is then subjected to a pressure of 3000-3500 p.s.i. for about 15 seconds, or of such duration to permit excess binder to flow from the mold. The molded mass is then removed from the mold and dried for about 16 hours at about 50 C. The dried mass is next machined to form any recesses therein which were not formed by the use of cores. The projectile is secured in place by the cement as aforementioned. Within the primer recess is inserted 0.9 grain of lead styphnate primer mix which is surmounted by a phosphorous-chlorate percussion cap of the general type used in cap pistols.

Our molded propellant for a 7.62 mm. has a length of about 1.650 inches, a base diameter of about 0.470 inch, a bore about of an inch in diameter by about 1% inches in length, a primer recess of 0.213 inch in diameter by a depth of about 0.065 inch and a bullet pocket of 0.309 inch in diameter by a depth of about 0.312 inch.

We claim:

1. An integrated, caseless molded small arms round possessing ballistic equivalency of a metal cased round of the same caliber comprising granules of propellant bonded in a molded mass by a low nitrogen nitrocellulose binder, said caseless round having a length and outside diameter similar to a same caliber metal cased round, said caseless round having a forward recess and a rearward recess, a projectile adhesively secured in said forward recess and a combustible primer mounted in said rearward recess, an axial cavity within said caseless round extending from the forward recess short of said rearward recess, a wall comprising said molded, propellant formed by said cavity and rearward recess, said wall supporting said primer when impacted by a firing pin.

2. The device of claim 1 further characterized by the adhesive securing the projectile in the forward recess of the round being a combustible nitrocellulose dissolved in a ketone.

3. The device of claim 1 further characterized by said axial bore having a diameter of approximately one-half the diameter of said caseless round.

References Cited by the Examiner UNITED STATES PATENT SAMUEL FEINBERG, Primary Examiner.

20 BENJAMIN A. BORCHELT, Examiner. 

1. AN INTEGRATED, CASELESS MOLDED SMALL ARMS ROUND POSSESSING BALLISTIC EQUIVALENCY OF A METAL CASED ROUND OF THE SAME CALIBER COMPRISING GRANULES OF PROPELLANT BONDED IN A MOLDED MASS BY A LOW NITROGEN NITROCELLULOSE BINDER, SAID CASELESS ROUND HAVING A LENGTH AND OUTSIDE DIAMETER SIMILAR TO A SAME CALIBER METAL CASED ROUND, SAID CASELESS ROUND HAVING A FORWARD RECESS AND A REARWARD RECESS, A PROJECTILE ADHESIVELY SECURED IN SAID FORWARD RECESS AND 